79 lines
1.5 KiB
Go
79 lines
1.5 KiB
Go
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// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import "os"
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type (
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processFn func(r result)
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inputFn func(processFn) error
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outputFn func([]result) error
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filterFn func(result) (include bool)
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groupFn func(result) (key string)
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)
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type pipeline struct {
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read inputFn
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write outputFn
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filter filterFn
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group groupFn
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}
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func (p *pipeline) filterBy(f filterFn) *pipeline { p.filter = f; return p }
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func (p *pipeline) groupBy(f groupFn) *pipeline { p.group = f; return p }
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func (p *pipeline) from(f inputFn) *pipeline { p.read = f; return p }
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func (p *pipeline) to(f outputFn) *pipeline { p.write = f; return p }
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func (p *pipeline) defaults() {
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if p.filter == nil {
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p.filter = noopFilter
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}
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if p.group == nil {
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p.group = domainGrouper
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}
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if p.read == nil {
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p.read = textReader(os.Stdin)
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}
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if p.write == nil {
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p.write = textWriter(os.Stdout)
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}
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}
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func (p *pipeline) start() error {
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p.defaults()
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// retrieve and process the lines
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sum := make(map[string]result)
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process := func(r result) {
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if !p.filter(r) {
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return
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}
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k := p.group(r)
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sum[k] = r.add(sum[k])
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}
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// return err from input reader
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if err := p.read(process); err != nil {
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return err
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}
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// prepare the results for outputting
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var out []result
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for _, res := range sum {
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out = append(out, res)
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}
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// return err from output reader
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return p.write(out)
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}
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